Mild, Rapid, and Inexpensive Microwave-Assisted Synthesis of Allylic and Propargylic Esters

Gill, Monica A.; Manthorpe, Jeffrey M.

doi:10.1080/00397911.2011.640970

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…It was envisioned that the desired substrates could be prepared from an esterification of 6 , followed by a sulfide to sulfone oxidation, and alkylation (Figure ). The esterification was more challenging than anticipated, with most standard methods failing.…”

Section: Resultsmentioning

confidence: 99%

“…Several mixed anhydride methods were attempted (ethyl chloroacetate, phenyl chloroacetate, and Boc 2 O) but were plagued by the displacement of allyl alcohol by the corresponding alcohol generated from the mixed anhydride (ethanol, phenol, and tert -butanol, respectively). Armed with the understanding of the strong tendency for the allylic ester products to undergo transesterification, a new mixed anhydride esterification method, promoted by microwave irradiation, was developed specifically for this work . Use of a pivaloyl mixed anhydride suppressed transesterification and provided synthetically useful amounts of the desired allylic esters; beneficially, this method required only 1 equiv of the allylic alcohol, which was quite useful when using more precious allylic alcohols.…”

Section: Resultsmentioning

confidence: 99%

“…High-resolution mass spectrometry (HRMS) was performed on a Kratos Concept-11A mass spectrometer with an electron beam of 70 eV at the Ottawa-Carleton Mass Spectrometry Center at the University of Ottawa, on a Bruker maXis impact Quadrupole-time-of-flight mass spectrometer in the positive ESI mode at the McGill Chemistry Mass Spectrometry Center, or a Sciex QSTAR XL hybrid quadrupole time-of-flight mass spectrometer in the positive ESI mode at the Carleton Mass Spectrometry Center. Compounds 1–2 , 3–5 , 6 , 7a–c , and 7e were prepared and characterized as previously reported.…”

Section: Methodsmentioning

confidence: 99%

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Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones and Identification of Unusual Side Products

Gill

Manthorpe

2019

J. Org. Chem.

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The use of sulfones as electron-withdrawing groups in substrates for palladium-catalyzed decarboxylative allylation was explored. A previously published trifluoromethanesulfonyl-based substrate was highly reactive and selective under mild conditions, but the substrate scope was not readily expanded. Instead, 3,5-bis(trifluoromethyl)phenyl sulfones were employed, thereby simultaneously retaining most of the electron deficiency and providing facile synthetic access. Optimization of the catalytic conditions to maximize the product distribution to a synthetically useful level of the allylation product over the protonation side product proved extremely challenging, with inconsistent and irreproducible results afforded with Pd 2 (dba) 3 as the palladium source. A variety of substrates were subjected to the optimized catalytic conditions of PdCp(1-cinnamyl) and Xantphos in tetrahydrofuran at 50 °C for 30 min. These conditions were applicable to all substrates with the exception of the α,α-dimethyl allyl ester, which required more forcing conditions and afforded four products: the allylation and protonation products, as expected, along with a cyclopropylation product and an unprecedented pseudodimeric product. The mechanism for the formation of these unusual side products is considered.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones and Identification of Unusual Side Products

Gill

Manthorpe

2019

J. Org. Chem.

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“…Given the simplicity and ease of this methodology, coupled with its low cost, we published this work in 2013. 81…”

Section: Substrate Scopementioning

confidence: 99%

Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones: Method Development and Mechanistic Studies

Gill¹

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Palladium-catalyzed decarboxylative allylation is a powerful method of carbon-carbon bond construction. This methodology relies on an electronwithdrawing group to promote the reaction. The use of sulfones in decarboxylative allylation has been explored using the trifluoromethylsulfonyl (triflyl) group, as well as the bis(3,5-trifluoromethyl)phenylsulfonyl (BTMP) group. These substrates are highly reactive at room temperature (triflyl) and 50 o C (BTMP sulfones). A detailed mechanistic study using deuterium-labelled substrates was performed to understand the origin of the protonation side-product. It was proposed that a βhydride elimination from the η 1 allyl on palladium could generate a palladium hydride intermediate along with an allene. Although small amounts of deuterium incorporation were observed in the protonated products, the proposed mechanism could not be the major pathway. Using isotopically labelled ligand, however, all protonation was supressed. This suggests that the origin of the proton is actually from the ligand and that kinetic isotope effects may be responsible for inhibiting the protonation pathway with labelled ligand. HRMS: m/z calcd for C14H12O2F6S: 358.0462; Found: 358.0454. But-2-en-1-yl-2-((3,5-bis(trifluoromethyl)phenyl)thio)acetate (3.37) Reaction Time & Temperature: 45 min, 80 °C Base: Pyridine Yield: 75%.

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ChemInform Abstract: Mild, Rapid, and Inexpensive Microwave‐Assisted Synthesis of Allylic and Propargylic Esters.

Gill

Manthorpe

2013

ChemInform

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Mild, Rapid, and Inexpensive Microwave-Assisted Synthesis of Allylic and Propargylic Esters

Cited by 4 publications

References 13 publications

Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones and Identification of Unusual Side Products

Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones and Identification of Unusual Side Products

Development of Palladium-Catalyzed Decarboxylative Allylation of Electron-Deficient Sulfones: Method Development and Mechanistic Studies

ChemInform Abstract: Mild, Rapid, and Inexpensive Microwave‐Assisted Synthesis of Allylic and Propargylic Esters.

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